The present invention relates to a flat panel display device having electron beam guides and particularly to a display device which includes means for modulating the electron beams.
U.S. Pat. No. 4,031,427 to T. O. Stanley, issued June 21, 1977, entitled "Flat Cathode Ray Tube" describes a flat cathodoluminescent display device which includes in an evacuated envelope, beam guides extending along the back wall of the envelope, and a gun structure which generates electrons and directs the electrons as beams into the beam guides. The beam guides confine and focus the electrons in the beams as the beams travel along paths parallel to the front wall of the envelope. The beams may be selectively deflected toward a phosphor screen on the front wall at selected points along the paths of the beams.
U.S. Pat. No. 4,088,920 to W. W. Siekanowicz et al., issued May 9, 1978, entitled "Flat Display Device with Beam Guide" describes a beam guide for use in the display device of the type described in U.S. Pat. No. 4,031,427. The beam guide includes a pair of spaced, parallel plates extending along and spaced from the back wall of the envelope. The plates have a plurality of aligned openings therethrough with the openings being arranged in rows extending longitudinally along the paths of the beams. Each longitudinal row of the openings constitutes a separate beam guide.
U.S. Pat. No. 4,121,130 of R. A. Gange, issued on Oct. 17, 1978, entitled "Cathode Structure and Method of Operating the Same", and copending applications for U.S. Patents, Ser. No. 835,772 of C. H. Anderson, filed Sept. 22, 1977, entitled "Beam Guide for Display Device with Beam Injection Means", now Pat. No. 4,128,784, and Ser. No. 921,267 of C. H. Anderson et al., filed July 3, 1978, assigned to the same assignee as the instant application, entitled "Guided Beam Display Device", disclose gun structures for use in the display device of the type described in U.S. Pat. No. 4,031,427. The gun structures include a line cathode having a plurality of modulation electrodes spaced along the line cathode. Potentials applied to the modulation electrodes cause the electrons generated by the cathode to be emitted therefrom in the form of beams. The gun structures may include isolation electrodes between the modulation electrodes to assist in confining and guiding the beams emitted from the gun structures into the beam guides.
In the gun structure of the Anderson application, Ser. No. 835,772, the modulation electrodes must be accurately dimensioned and positioned with respect to the beam guides. Tabs which are aligned with a separate longitudinal row of openings in the beam guide plates project from the ends of the beam guide plates adjacent the gun structure and allow the creation of an acceleration field which draws electrons between the guide plates and along the longitudinal row of guide plates openings. However, if the edges of the two overlapping modulation electrodes which face the guides do not have a similar contour and are not equidistant from the guide, the beam will be pulled off center and will not enter the guide properly. Therefore, during the fabrication of the display device, the modulation electrodes must be positioned with a high degree of accuracy.
In the gun structure of the Anderson et al. application Ser. No. 921,267, the modulation electrodes and isolation electrodes partially overlap the beam guide to eliminate the deleterious effects of differences in the contour or misalignment of the edges of the overlapping electrodes.
In each of the above-indicated copending applications, and in the Gange patent, the modulation and isolation electrodes are mounted on discrete pads on the walls of a U-shaped support which opens toward the beam guide. The electrodes comprise a layer of tantalum deposited on the pads. The accuracy with which beams of electrons enter the guide is determined by the accuracy with which the opposing pads and tantalum electrodes deposited thereon are aligned.